A CCTV camera multiplexer is an electronic unit that is able to combine the video transmission signals from more than one camera into one single channel or transmission. These units are often used where processors, VCRs, Digital Video Recorders or DVRs, and monitors can only handle one input. The multiplexer, also known as a Mux, in essence reduces the multiple camera feeds by creating one output that combines all of the inputs to the multiplexer.